by Aamer Madhani and Alan Gomez, USA TODAY

by Aamer Madhani and Alan Gomez, USA TODAY

WASHINGTON - The White House on Monday pushed back against suggestions from some Republican lawmakers that last week's bombings at the Boston Marathon should slow down the conversation on an overhaul of the nation's immigration laws.

Sen. Rand Paul, R-Ky., suggested on Monday that last week's bombings - which authorities suspect was carried out by two young Chechen immigrants - casts a shadow on the immigration debate.

"Before Congress moves forward, some important national security questions must be addressed," Paul wrote in letter to Senate Majority Leader Harry Reid. "The facts emerging in the Boston Marathon bombing have exposed a weakness in our current system. If we don't use this debate as an opportunity to fix flaws in our current system, flaws made even more evident last week, then we will not be doing our jobs."

White House Press Secretary Jay Carney responded to reporters on Monday that the administration believes that "one of the reasons we need comprehensive immigration reform is because it will enhance, when implemented, our national security."

Authorities on Monday charged 19-year-old Dzhokhar Tsarnaev in the double bombing. His 26-year-old brother, Tamerlan, who died in a shootout with police, is also suspected by authorities for the blasts, which killed three and wounded 170 others near the marathon's finish line. Both have roots to war-torn Chechnya but came to the United States a decade ago.

A heated exchange between lawmakers also loomed large in a Monday meeting of the Senate panel that is debating changes to the country's immigration laws.

Sen. Patrick Leahy, D-Vt., chairman of the Senate Judiciary Committee, opened the hearing by accusing Republicans of exploiting the Boston Marathon attack to try and slow down progress on a sweeping immigration bill.

Leahy was responding to comments made by Sen. Chuck Grassley, R-Iowa, last week. Grassley, the ranking Republican on the committee, said that Congress should move carefully with the immigration bill after it was learned that the two suspects in the Boston Marathon were immigrants.

Leahy, and Sen. Charles Schumer, D-N.Y., said it was irresponsible to use that tragedy as an excuse to derail the progress made on an immigration bill that would allow up to 11 million unauthorized immigrants to become legal residents and further secure the nation's borders.

"Let no one be so cruel as to try to use the heinous acts of two young men last week to derail the dreams and futures of millions of hardworking people," Leahy said. "The bill before us would serve to strengthen our national security by allowing us to focus our border security and enforcement efforts against those who would do us harm."

Grassley, sitting y next to Leahy in the committee room, responded that he never accused anyone who sought gun-control legislation of politicizing the Newtown massacre.

Grassley added that he never accused anyone of politicizing the explosion in a West, Texas, fertilizer plant who want to know if we're doing enough to ensure that such facilities are safe enough.

"I think we're taking advantage of an opportunity‚?¶to make sure that every base is covered," Grassley said.

Grassley and Schumer also had a sharp exchange after the senator from New York said the lawmakers bringing up Boston are using it as an "excuse for not doing a bill or delaying it."

An irritated Grassley interjected several times, saying, "I never said that."